The use of a PTO device in association with truck or other vehicle (or stationary engine) transmissions is generally known. Such PTO devices often include an input gear, an output gear and a mechanism for engaging the input gear with the output gear so as to rotate the output shaft of the PTO device to power an auxiliary device to perform useful work when desired. The mechanism also provides a means for disengaging the input gear and the output gear.
In certain conventional designs, the input gear of the PTO device is constantly engaged with the appropriate gear in the vehicle's transmission when installed on the vehicle and is, thus, continuously turning whenever that corresponding gear in the vehicle's transmission is turning. In order to provide for selective rotation of the output shaft of the PTO device (associated with the output gear), a clutch mechanism is frequently provided between the input gear of the PTO device and that output gear. When this output shaft is rotated, useful auxiliary work can be performed. For example, the output shaft may be connected to a hydraulic pump that may be used to operate auxiliary equipment, such as garbage compacting bodies, dump bed bodies (a/k/a, “dump trucks”), garbage trucks or trailers, buckets for elevating working personnel, winches, post hole diggers, and the like.
In one conventional example the PTO device clutch is operated through an aligned multi-disc stack arrangement located between the shaft of the PTO device, and the gears of the PTO device engage their respective gears of the truck's transmission. When an axial force is applied to the disc stack, frequently by overcoming an oppositely directed biasing force typically provided by a spring, the individual discs in the stack are forced together such that the interfacial friction between the discs cause the shaft to be rotationally joined to the rotating gears.
In a typical arrangement with a PTO device connected to an engine, the circulation of cooling and lubricating fluid through the PTO device is powered by, and therefore typically controlled by, the engine transmission's circulation pump.